This invention relates to OTP (One-Time Programmable) memory cells and their memory arrays and, in particular, to using the inherent variations in the programmability of OTP memory cells in an array for PUF (Physical Unclonable Function) security.
The random variability of some semiconductor device parameters has been used or considered for security applications. These parameters include the threshold voltage VT of MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), the on-current, and metal resistance. However, due to various semiconductor mechanisms, such as Hot Carrier Injection (HCI), Time-Dependent Dielectric Breakdown (TDDB), ElectroMigration (EM), the constancy of these parameters over the time is problematical and correspondingly can cause a deterioration of the PUF in the semiconductor device. Furthermore, with constant improvements in semiconductor process control, process variations are reduced rendering PUF signals based upon these parameters more and more difficult to distinguish.
Hence what is desirable is a semiconductor device parameter which is variable with PUF signals based upon that parameter which unlikely to deteriorate over time. The present invention provides for such a semiconductor device parameter which can be used to generate PUF signals which are unlikely to change.